Square wave generator with impulse counter timing control for frequency division



Nov. 29, 1949 E. R. SHENK 2,489,824 SQUARE WAVE GENERATOR WITH IMPULSE COUNTER TIMING CONTROL FOR FREQUENCY DIVISION Filed Dec. 24, 1943 2 Sheets-Sheet 1 INPU T l lllllllll IIIIIIII will IN VEN TOR.

vyw

ATTd/VEY- Nov. 29, 1949 E. R. SHENK SQUARE WAVE GENERATOR WITH IMPULSE COUNTER Filed Dec. 24, 1943 TIMING CONTROL FOR FREQUENCY DIVISION 2 Sheets-Sheet 2 INVENTOR. Eugerw 12/. Sharpie rromvsr.

Patented Nov. 29, 1949 UNITED STATES PATENT Eugene R. Shenk, Brooklyn, N. Y., assignor to OFFICE Radio. Corporation of America, a corporation of Delaware Application December 24, 1943, Serial No. 515,470

8 Claims.

This invention relates to frequency dividing circuits. Counting circuits of .various types are well known in the art and are frequently used as frequency dividers.

,Heretofo're frequency dividers have possessed trol of aperiodic impulses.

ing drawings, in which:

period of oscillation;

vision of back-to-back interaction between two gaseous discharge tubes of its locking circuit; and Fig. 4 shows a novel form of counting circuit per se.

Referring first to Fig. 1, I show therein a cir- Anode potential is 6 and one The cathode 9 in tube This capacitor l I is also con- The same source can be 5 the disadvantage of operating at a natural frecuit arrangement comprising a discharge tube I, quency of their own in the absence of a controlwhich may be used for amplifying the waves of ling frequency. Alsosmall variations of the ciran input potential. This tube is provided with an cuit constants, or of the amplitude of the controlinput circuit comprising resistors 2 and 3 serially ling frequency; were likely to change the order 10 connected between the cathode and control grid. of division. A further disadvantage is that the Input potentials of any frequency or even aperiorder of division is a function of the controlling odic impulses are applied at the junction between frequency. The multivibrator and the blocking the two resistors 2 and 3. oscillator are examples of frequency dividers of supplied through aresistor 4. this type. A twin diode tube 5 has one anode One type of frequency divider that does not cathode 1 coupled to the anode circuit of tube I possess a natural frequency of its own is the sothrough capacitor 8. called "counter circuit. In this circuit the voltis grounded, as is the cathode in tube l. The age across a condenser is built up in steps (one anode It] in tube 5 is coupled to ground through step for each cycle of the controllin frequency) a capacitor ll, until it reaches a critical value, at which point it nected between ground and the cathode of a disac'tu'ates a blocking oscillator which oscillates for charge tube l2, the latter being one of two tubes a very short time and discharges the condenser. connected in a well-known locking circuit. The Then the voltage stepping or counting process other tube l3 in this circuit has a cathode which begins all over again; The output of the divider is directly grounded. is, therefore; limited to a short pulse occurring Positive potential is supplied from a suitable at some submultiple of the controlling frequency. direct current source to the anode of tube l2 It is an object of my invention to provide a through resistor l4. frequency divider circuit which has no natural used to supply potential to the anode of tube [3 frequency of its own,.i'. e.; it must be driven. through resistor l5.

Another object is to provide a locking circuit The anode in tube I2 is coupled through cafor counting purposes which functions under conpacitor Hi to the control grid in tube l3. A resistive connection including resistor I1 is made Still another object is to provide a frequency between the anode of tube l3 and the control grid divider circuit of simple design capable of useful of tube l2. operation under widely varying conditions. The control grid in tube I2 is preferably nega- A more specific object of my invention is to tively biased with respect to ground, this being provide a rectangular wave generator which is accomplished by means of a negative biasing subject to control by alternating current waves source I8, the negative terminal of which is conof a given frequency harmonically related to the nected through resistor 19 to the grid in tube cyclic period of the rectangular wave output, I2. The control grid in tube 13 is connected to where such output is composed of flat Wave ground through a resistor 20. crests (or inesas) and valleys, the timeratio In the operation of the circuit arrangement between which is adjustable in accordance with shown in Fig. 1; capacitor II is used for triggerthe ratio between any twosmall integers. ing the locking circuit by building up a negative My invention will now be described in more voltage on the cathode in tube l2. The actual detail, reference bein made to the accompanytripping of the trigger is, however, delayed for a number of counting impulses delivered through Fig. 1 shows the combination of a counting the input circuit of tube I until the desired numcircuit with a locking circuit having no natural ber of impulses has been counted. Consider first that the counting cycle commences with a pulse Fig; 2 shows a modification wherein the eonof negative polarity so as to bias the grid in tube trol pulses can be applied in two different phases; l to cut-off. Each such impulse raises the anode Fig. 3 shows another circuit having the contrapotential in this tube to that of the direct current source and a positive charge is supplied to capaciinasai control feature of. Fig. 2, but with the pm 3 tor 8. The charging circuit traverses the left hand section of tube wherein the space path between cathode 9 and anode 6 becomes conductive.

During the positive half cycle of the counting impulse, tube I becomes conductive. Capacitor 8 discharges by virtue of a conductive state which occurs between the cathode I and anode II] in the right hand section of the tube 5, and this action produces an increment of negative charge on the ungrounded side of capacitor II. The step-by-step accumulation of charges on capacitor I I takes place until the threshold bias in tube I2 is overcome. Tube I2 then becomes conductive. The circuit constants are so chosen that the desired number of control impulses may be counted during the build-up of charges on capacitor I l to the triggering level.

During the conductive state in tube I2, the charge on capacitor II is dissipated and thereafter current flows through the two space paths of tube 5 as a series circuit to ground. After a period of time determined primarily by the values of capacitor I6 and resistor 25, the conductive state ceases in tube I2 and the counting process repeats itself.

Output potentials may be derived from any suitable point in the circuit, but for the sake of illustration, the output is shown as taken oil from the anode in tube I3 through coupling capacitor 2|. In order to satisfy certain utilization requirements, the output may, however, be derived from a point such as the connection between the resistor I 4 and the anode in tube I2.

Referring now to Fig. 2, I show a circuit arrangement which is similar in many respects to that of Fig. 1. There are two counting circuits both exactly the same as the one shown in Fig. 1. Like parts are given like reference numbers. Certain of the symmetrically disposed parts are distinguished by affixing the prime to the reference number for the right hand element.

The tubes 22 and 23 are shown as pentodes. Tube 23 has its own triggering circuit comprising discharge tube I and twin diode tube 5.

These tubes occupy positions which are the counterparts of tubes I and 5 and are used for pro-, viding dual control of the locking circuit. The symmetrical relationship between the two counting circuits may readily be seen. Tube I" has an input circuit comprising resistors 2 and 3' and the junction between these two resistors has a connection to a source of input potentials which under certain conditions may be 180 phase displaced with respect to the input potentials applied to tube I. Such contraphasal relationship may, for example, be obtained by the use of a transformer, the secondary of which has its outside terminals connected one to the input circuit of tube I and the other to the input circuit of tube I' while the center tap is grounded.

The anode in tube 22 is connected to the grid in'tube 23 through a resistor 26. The biasing source I8 is used to apply the same negative bias to the control grids in tubes 22 and 23 so that these tubes operate in balanced relationship to one another.

If each portion of the triggering circuit of Fig. 2 is to count by an integer, the input pulse should be supplied in the same phase to both inputs. If, however, each portion of the circuit is to include a fraction of a tone cycle in its count, then the phase of the input potential applied to tube I must be different from that which is.

applied to the input circuit of tube I. If one portion of the circuit includes in its division a certain fraction, 1', of the period of the applied input tone frequency, then the other portionmust-and automatically Willinclude the complementary fraction (1r) in its division. The order of division of the circuit as a whole will always be an integer. The difference between phase #1 (applied to tube I) and phase #2 (applied to tube 2) must be 360 r degrees.

The count obtained by means of either of the circuits of Figs. 1 and 2 can be adjusted by varying the values of the anode potential source or the grid biasing source or both. However, changing either of these voltages results in a similar change in the action of both tubes 22 and 23. This is sometimes undesirable since under these conditions changing the count of one tube by variation of one of its supply voltages will also alter the count of the other tube. This same interlocking is experienced if the count is varied by means of changes in the values of resistors I9, 20, 26, and 21.

A preferred means of adjusting the count is by varying the load resistors I4 and I5. An advantage of this adjustment is that the value of resistor I5, for example, will change the net grid voltage applied to the grid in tube 22 when this tube is non-conducting, but the same adjustment will have a negligible effect on the grid volt age when the tube is conducting. Thus, if rcsistor I5 is much less than the combined resistive values of elements I9 and 21, the count of tube 22 will increase and decrease in accordance wit the value assigned to resistor I5.

Furthermore, if the value of resistor I4 is much less than the combined ohmic values of resistors 20 and 26, then the count of tube 23 will vary with the value of resistor I4. In a pentode tube the D. C. anode current is independent of the value of the anode load resistor over a wide range. Therefore, the method of adjusting the count as above described is especially successful with pentodes.

The circuit arrangement of Fig. 3 is one which provides a number of advantageous features among which may be mentioned the following:

It is arranged with a pair of gaseous discharge tubes 3| and 32, the anodes of which are inter-' coupled by means of a capacitor 33 for so-called back-to-back" interaction. This circuit has no natural period of its own but must be driven by external control voltage. It delivers a substantially rectangular waveform output voltage. It is very conveniently and simply adjusted to count impulses within a considerable range. The ratio is adjustable between the number of impulses counted on the positive half cycle as compared with the negative half cycle of output voltage. The order of count is independent of the input frequency over a number of octaves.

The circuit connections as shown in Fig. 3 are substantially identical with those of Fig. 2 except that in Fig. 3, I preferably provide two ad-' justable potentiometers 34 and 35 for independently controlling the quiescent bias on the grids of tubes 3I and 32 respectively. The operation of the circuit of Fig. 3 will be readily understood in view of the foregoing description of Figs. 1 and 2.

In accordance with the well-known manner of igniting and extinguishing two back-to-backconnected thyratron tubes, such as tubes SI and 32, it will be remembered that when either of these tubes ignites the surge impulse impressed ac ss arasites 3. e he ea -2s is A ng shed fict is readi -Y d st 'of the ta n o mp ses-e uat y is? 1 511 3:

potentiometer l ewise, tiihumber of 'im pulses counted during the period of non-conduction in tube 3? is determined by the adjustment of the tap on potentiometer 35:. The anode voltage applied to tube I may or may not be quaito L that which is applied to tube 3!. "The reliability of the count can be increased by increasing the anode voltage applied tothe an'o'de'of tube Fig. 4 shows an embodiment or my invention which comprises the same counting air "itlets shown in the other figures, but this is operat ve- 1y? associated with a blocking oscillator. lhe'iiscillater tube 4| has its anode circuit or'inectd through the primary winding 43 'ofa transformer T, and thence to the positive terminal of'a direct current source. The grid of tube 4| is connected through the secondary 42 of the same transformer and thence to a ground connection through tap 41 which is adiustably associated with a potentiom t r 4B- Across the terminals of p tentiomet 6. I p f rably conne t a bias sour e 58- In his manner the l?- C- bi s vo t appli d to th ri t be A! may b suitabl ust d- .A bypass condenser 45 is connected between the tap 41 and ground, thus shunting the grounded portion of potentiometer 46.

In the operation of the circuit arrangement shown in Fig. 4, a negative charge on capacitor 44 is built up in steps as determined by the impress of counting pulses via capacitor 8 and through the right hand section of the rectifier tube 5. Upon the occurrence of a certain step, the cathode in tube 4| will be rendered sufficiently negative so that this tube will oscillate and its anode and grid current will discharge the capacitor 44. The number of the count is determined by the setting of the potentiometer tap 41.

While I have shown and described a number of different embodiments of my invention, it will be seen that there is a common basic principle which is inherent in all of the circuit arrangements.

Other modifications of my invention will doubtless suggest themselves to those skilled in the art in view of the foregoing description.

I claim:

1. A frequency divider circuit arrangement comprising a pair of discharge tube structures each having a cathode, an anode and a control grid, a direct current energy source having a grounded negative terminal and resistive connections from its positive terminal to each of said anodes, two capacitors each individually coupling one of the cathodes respectively to ground, an inter-control impedance network constituting means for causing each tube structure when it is conductive to render the other tube structure non-conductive, and two impulse counting circuits each separately associated with a respective one of said capacitors and arranged to build up incremental charges therein, said counting circuits being further characterized in that each offers a unidirectionally conductive path to ground from a respective one of said cathodes.

2. A circuit arrangement according to claim 1 and including on said inter-control network two resistors each interconnected between the anode of one tube and the control grid of the other tube, and means for applying to each of said grids a negative direct current bias with respect to ground.

3- A ircu t a rsns 1 in -\ivhi'ch said'tubes and said inter ccontrol A v g I Le it f ifii eurilifis th a i ht o tubesln gtaligularwav generator subject to control byan ezrtern'al source tralternatmgcur; i}, an elegtr mqcdunung circuit arranged and as m count watercress miscreants:

ea nrfedeternmednm n ervene 's'e" as gelt nic counting"circuit'arrangd arid ad ed the nameless: b pb i bb ar y .-T is a; mm d ately" snowin p e m time interval, each r said 'um ng "circuits in; v:el e t i whi h n' ehie alcha a e bu lt 11 2 by War o i e a in t f 'r s 'f said .1%, cy l s their 6i tea e s d schar e use 9? th 'i 'ie etyrsfa fi r s te rev's r hence 'el i i n a ive rm e and fiar'et resistive 'cqnhe ti ns from its'positive'terfiiinal to each of the anodes in saidtubesfa condenser intercouplingsaid anodes, "and means "for can ingeach 'df' said timeintervals as measured by said'couriting circuits t9 be terminated by discharge ofan alternate one er ssid'capacitsrs through the ionization path of a respective tube.

{i In a rectangular wave generator subjectto control by an external source of'alternatin'g' cur rent, a pair of gaseous discharge tubes each having a cathode; an anode and a control grid, means for applying an independently adjusted negative bias to the grid with respect to the quiescent-state potential of the cathode in each tube, unidirectionally conductive devices individually connecting said cathodes to ground, a capacitor in shunt with each said device, a direct current operating potential source connected between said anodes and ground, a load impedance connecting each anode to said source, a condenser interooupling said anodes and constituting means for reciprocally extinguishing each tube when the other ignites, means for incrementally charging each said capacitor from uni-polar half cycles of said alternating current, the operation of said means being effective after integration of a predetermined number of halfcycle charges to ignite the gaseous tube with which the particular capacitor is connected, thus causing said capacitor to discharge through said gaseous tube.

6. Apparatus for producing a rectangular wave having a desired time relation between the mesa-portion and the valley-portion of each cycle, said time relation being determined by a suitable choice of circuit parameters in an electronic generator of such a wave, where said generator is subject to control by two separate counting circuits, one for timing the mesa-portion and the other for timing the valley portion of said wave, said apparatus comprising means for causing each of said counting circuits to store a succession of capacitive charges which are derivable from uni-polar half cycles of a given alternating current, said counting circuits being successively operable, means for producing an ionization discharge which dissipates the energy of the stored capacitive charges of one counting circuit and terminates one count of half cycles, means for producing a second ionization discharge which dissipates the energy of the stored charges of the other counting circuit, thus terminating the other count of half cycles, and means for deriving said rectangular wave from potential variations which are due to the alter- 7 nately successive occurrences of the first and the second ionization discharges.

7. A frequency divider comprising a pair of electron discharge device structure Whose electrodes are interconnected to provide a circuit of two degrees of electrical stability, such that one structure is conductive when the other structure is non-conductive for one degree of electrical stability, and vice versa for the other degree of electrical stability, separate impulse counters coupled to said structures, each counter adapted to change the condition of stability of said devices after a predetermined count, and means for varying the interval of conductivity of one structure relative to that of the other structure over a complete cycle of operation of said circuit.

8. A frequency divider comprising a pair of gaseous tubes each having an anode, a cathode and a grid, commutating condenser coupled between the anodes of said tubes, separate potentiometers for the grids of said tubes for individually adjusting the bias thereon, a condenser coupling the cathode of each tube to ground, and a source of anode polarizing potentials for said tubes, whereby said pair of tubes constitute a circuit having two degrees of electrical stability in which one tube is conductive and the other tube non-conductive for one degree of stability,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,059,562 Curtis et a1 Nov. 3, 1936 2,113,011 White Apr. 5, 1938 2,122,464 Golay July 5, 1938 2,185,199 Kahn Jan. 2, 1940 2,185,363 White Jan. 2, 1940 2,193,850 Andrieu Mar. 19, 1940 2,258,943 Bedford Oct. 14, 1941 2,403,615 Sanders, Jr July 9, 1946 2,418,521 Morton et al Apr. 8, 1947 2,421,018 Rosa May 27, 1947 2,430,547 Anderson et a1. Nov. 11, 1947 2,442,256 Bartlett May 25, 1948 2,442,403 Flory et a1 June 1, 1948 2,452,549 Cleeton Nov. 2, 194.8 

